The use of input/output terminals to communicate interactively with a data processing system is now becoming commonplace. At present most communication takes place through a v.d.u. such as the IBM 3278 data display terminal (IBM is a Registered Trade Mark) which has a keyboard for the operator to enter information and a cathode ray tube (c.r.t.) on which both the entered information and the data processor's response are displayed.
In many applications, however, the operator does not look at the c.r.t. screen continuously, such as when entering a continuous text stream, or when an associated manufacturing operation only requires messages to be infrequently displayed on the screen. Blind or partially sighted operators or users of the system also do not find the need to use the screen for an indication of output messages helpful.
The present invention is directed towards providing a terminal device for a data processing system which provides an audio output for information entered into and messages received from the data processing system.
The terminal may be a pure audio response unit, or the audio response unit may be combined with a v.d.u. or any other data output device.
Devices are known in which audio responses are made to operator's specific requests. These have until now been of the type in which a large dictionary of words or syllables is recorded on an audio recording medium such as magnetic tape or digitally on a disc and the data processor constructs an audio response by selecting the appropriate words or syllables and concatenating them. There is an inherent limitation in this approach as any response may only use what has already been recorded and new words and combinations cannot be used. The system also has a large storage requirement which is an unacceptable overhead.
The present invention makes use of a phoneme-based speech synthesizer such as that described in published Great Britain Patent Application 2,077,558 (Federal Screw Works). This patent application describes a phoneme-based speech synthesizer that is particularly adapted for implementation on a single integrated circuit chip includes a vocal tract model comprised of a fixed resonant filter and a plurality of tunable resonant filters whose resonant frequencies are controlled in accordance with the values of certain control parameters. A digital transition circuit is included which gradually transitions the values of the vocal tract control parameters as they change from phoneme to phoneme by iteratively adding to the current values a predetermined percentage of the difference between the current and target values. The vocal tract model is implemented utilizing a capacitive switching technique which eliminates the need for large valued components to achieve the relatively low frequencies of human speech. A glottal source generator is adapted digitally to generate a glottal pulse signal in a manner which readily permits the glottal pulse to be spectrally shaped in any desired configuration.